Everything Within Balance: As Predators Decrease, Ecosystems Suffer
April 10, 2012

Everything Within Balance: As Predators Decrease, Ecosystems Suffer

As predators dwindle in the Northern Hemisphere, populations of their would-be prey begin to flourish. A new survey suggests such large populations are harmful to their specific ecosystems.

Scientists from Oregon State University examined 42 studies from the past 50 years and found that as wolves disappear from the northern United States, Canada, and Alaska, populations of moose and deer swell. The resulting boom in moose and deer populations can be harmful to other living things in the ecosystem, such as trees and other plant life, reducing the amount of biodiversity. As fewer trees take root and flourish, the risk for deforestation increases, thus removing less carbon from the air and contributing to the negative effects of climate change.

The research has been published online in the European Journal of Wildlife Research.

Such a cause-and-effect sequence of events can be wide spread. In a press release, Lead author William Ripple, OSU professor of forestry, said, “These issues do not just affect the United States and a few national parks. The data from Canada, Alaska, the Yukon, Northern Europe and Asia are all showing similar results. There´s consistent evidence that large predators help keep populations of large herbivores in check, with positive effects on ecosystem health.”

According to their research, deer and moose populations were 6 times greater in areas without wolves than in areas with wolves. Additionally, their research found when two or more predators inhabit the same space, like bears and wolves, the population of mammalian herbivores are greatly moderated.

“Wolves can provide food that bears scavenge, helping to maintain a healthy bear population,” said Robert Beschta, a professor emeritus at OSU and co-author of the study. “The bears then often prey on young moose, deer or elk – in Yellowstone more young elk calves are killed by bears than by wolves, coyotes and cougars combined.”

In Europe, the same results were found. As wolves and lynx were found together, so too were the populations of herbivores kept in balance.

This survey brings to light the importance of every player in an ecosystem. When one or more aspect is thrown out of balance, the entire system feels the effect.

“In systems where large predators remain, they appear to have a major role in sustaining the diversity and productivity of native plant communities, thus maintaining healthy ecosystems,” said Beschta in a press release. “When the role of major predators is more fully appreciated, it may allow managers to reconsider some of their assumptions about the management of wildlife.”

One example of this kind of assumption can be found in Idaho and Montana, where wolves are being killed by the hundreds in an effort to reduce cattle conflicts and boost the population of game herds. According to this new research, these kind of actions could prove harmful to the surrounding ecosystems of Idaho and Montana.

According to the report, the human hunting of these predators may not even be an effective way to reduce the population, as “hunting by humans is often not functionally equivalent to predation by large, wide-ranging carnivores such as wolves.”

This research acts as further proof that everything within an ecosystem works together. Even though the wolves and predators seem like the bad guys, without them, the ecosystem on the whole can fail.